Photo-refractive keratectomy is fast becoming a popular surgical method of correcting sight disorders by removing a thin disc shaped layer of tissue in the center of the cornea using a laser beam which creates a new contour to the lens surface. Differing thicknesses of tissue are removed by causing the diameter of the laser beam to change, generally, from an initial central narrow beam, to a broader beam so that a lens shaped dish of tissue material is removed. Not only can myopia and hypermetropia or hyperopia be cured but also other defects such as astigmatism. (See, for example, The Excimer, Fundamentals and Clinical Use, Harold A. Stein et al, Slack Inc. 1994, pages 9-16).
In order to prepare an eye for such surgery it is necessary to remove the superficial cellular epithelium to expose the Bowman's layer of the predetermined region(s) of the cornea to be reshaped. Great care must be taken not to damage the subjacent Bowman's layer of the fibrous cornea.
Heretofore this superficial epithelium has been removed either by weakening the epithelium with alcohol, and then scratching away the soft tissue or alternatively, by scraping the epithelium using a sterile, spatulated scalpel.
Alcohol, however, has a tendency to cause slight swelling of the cornea which can prevent an accurate result from being achieved.
The spatula method, on the other hand, is a rather difficult technique and often causes damage to the underlying Bowman's layer or, more commonly, does not completely remove the epithelial layer. Small tags of epithelium remaining can result in uneven laser ablation.
It has also recently been proposed to use a rotatable brush of non-contiguous separated plastic self-supporting tapered pins, as derived from surgical hand scrubbing brushes, and to attach the same in line with a hand-held housing carrying a longitudinal rotating shaft. The surgeon applies the brush to the central area of the cornea causing the rotating pins to tear or rip away within 2-3 seconds the central portion of the epithelium--with the torn off epithelium caught between the pins for removal, as described in an article entitled "Rotating Brush for Fast Removal of Corneal Epithelium" by I. G. Pallikares et al, appearing in the Journal of Refractive & Corneal Surgery, Vol. 10, July/August 1994, pages 438-442.
While suggesting an important conceptual direction, this construction, however, introduces serious disadvantages including view-destruction by the presence during use of the longitudinal hand-held housing rearward of the brush, difficulty fitting, adjusting, tilting and operating in the limited space between the objective of the surgeon's operating microscope and patient's eye, and the resulting rough epithelial edges left by the torn off central epithelium portion.